Author Information

Intravascular optical coherence tomography (IV-OCT) has gained widespread use over the past few years, offering highly detailed images of coronary artery pathologies and interventions (1). In contrast to the cross-sectional view, longitudinal sections and 3-dimensional (3D) renderings are affected by cardiac motion artifacts and undersampling, complicating interpretation and measurements (2). We developed Heartbeat OCT, a new OCT method that achieves up to 4,000 frames/s imaging speed for isotropically sampled volume datasets acquired within the diastolic phase of 1 cardiac cycle to restore 3D IV-OCT image fidelity. In this research letter, we present the first in vivo data acquired with this new experimental technology.

We created an IV-OCT system that records a densely sampled dataset at a pull-back speed of 100 mm/s (3). It relies on a newly developed Fourier domain mode-locked laser (4), generating 2.88 million wavelength sweeps per second. The experimental catheter is distally actuated by a micro motor that can achieve a rotational speed of up to 4,000 revolutions per second in vivo. In vivo imaging experiments were conducted in a healthy swine. The electrocardiogram-triggered Heartbeat OCT pull-back acquisition took 0.5 s during the diastolic phase of a single cardiac cycle, avoiding the ventricular contraction that causes motion artifacts.

The frame pitch in a Heartbeat OCT pull back is equal to the transverse resolution, resulting in an image dataset that is adequately sampled in all dimensions (radial × angular × longitudinal). It represents not only the familiar arterial structures that are visible in cross-sectional images, but also allows unprecedented visualization of side branches and microscopic in 3D and longitudinal rendering as shown in the journal cover image. However, these features are normally washed out in the coarsely sampled commercial IV-OCT images. This experimental catheter presently lacks guidewire compatibility and shows shadows in 3D reconstruction due to the motor wires. These limitations will be addressed in near-future realizations of the device that will be miniaturized to 3-F or less and suitable for evaluation in human coronary interventions.

Heartbeat OCT provides comprehensive imaging of the coronary vasculature in vivo at microscopic resolution, aimed at characterization of coronary artery disease and guidance of coronary interventions. The scan rate of Heartbeat OCT (measured in samples per second) is greater than that of established technologies by a factor of 20 to 30 (Table 1). This gain in acquisition speed is used to shorten the imaging time and to improve longitudinal image quality. An additional potential advantage of the short imaging time is a reduction of the required contrast flush volume. Vessel geometry and length measurements are affected by cardiac motion in conventional OCT. High-quality 3D and longitudinal renderings are needed for post-intervention assessment of side branches—for example, in the presence of carina shift. The resulting 3D reconstructions of the healthy swine vessels appear smooth and tapered, evidence of a faithfully rendered luminal geometry without cardiac motion artifacts.

Footnotes

Please note: Drs. Wang, Regar, Beusekom, Lancee, Springeling, Krabbendam-Peters, van der Steen, and van Soest are from the Department of Cardiology, Erasmus University Medical Center, Rotterdam, the Netherlands; Drs. Pfeiffer, Wieser, and Huber are from Lehrstuhl für Biomolekuläre Optik, Fakultät für Physik, Ludwig-Maximilians-Universität Munchen, Germany; and Drs. Pfeiffer and Huber are from the Institut für Biomedizinische Optik, Universität zu Lübeck, Lübeck, Germany. This research was partly supported by the China Scholarship Council, the German Research Foundation (DFG-HU 1006/2, HU 1006/3, Cluster of Excellence: Munich Centre for Advanced Photonics), and the European Union (ERC, contract no. 259158). Mr. Wieser has a financial interest in Optores GmbH, which commercializes Fourier domain mode-locked technology for nonvascular applications. Prof. Huber has a financial interest in Optores GmbH; and holds a patent licensed to St. Jude Medical. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.

The authors acknowledge J. Meijer and B. Knapen from KINETRON B.V. for manufacturing the micro motor, and C. Niles and R. van Duin for their contributions in the animal experiment preparation and histology preparation.

American College of Cardiology Foundation

References

(2012) Consensus standards for acquisition, measurement, and reporting of intravascular optical coherence tomography studies: a report from the International Working Group for Intravascular Optical Coherence Tomography Standardization and Validation. J Am Coll Cardiol59:1058–1072.